From 756f5985b5e4ca0b08e60fff36ef3c51fb79de75 Mon Sep 17 00:00:00 2001
From: Fabian Ruhland <ruhland@hhu.de>
Date: Fri, 11 Oct 2024 14:27:53 +0200
Subject: [PATCH] config_tables: Skip ACPI entries with invalid RSDP version

---
 towboot/src/boot/config_tables.rs | 58 ++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 24 deletions(-)

diff --git a/towboot/src/boot/config_tables.rs b/towboot/src/boot/config_tables.rs
index 1cd32d5..017626e 100644
--- a/towboot/src/boot/config_tables.rs
+++ b/towboot/src/boot/config_tables.rs
@@ -14,8 +14,6 @@ use uefi::table::cfg::{
     SMBIOS3_GUID,
 };
 
-static mut RSDP_V2_SET: bool = false;
-
 /// Go through all of the configuration tables.
 /// Some of them are interesting for Multiboot2.
 pub(super) fn parse_for_multiboot(info_builder: &mut InfoBuilder) {
@@ -27,8 +25,8 @@ pub(super) fn parse_for_multiboot(info_builder: &mut InfoBuilder) {
     debug!("going through configuration tables...");
     for table in config_tables {
         match table.guid {
-            ACPI_GUID => handle_acpi(&table, info_builder),
-            ACPI2_GUID => handle_acpi(&table, info_builder),
+            ACPI_GUID => handle_acpi_v1(&table, info_builder),
+            ACPI2_GUID => handle_acpi_v2(&table, info_builder),
             DEBUG_IMAGE_INFO_GUID => debug!("ignoring image debug info"),
             DXE_SERVICES_GUID => debug!("ignoring dxe services table"),
             HAND_OFF_BLOCK_LIST_GUID => debug!("ignoring hand-off block list"),
@@ -42,33 +40,45 @@ pub(super) fn parse_for_multiboot(info_builder: &mut InfoBuilder) {
     }
 }
 
-/// Parse the ACPI RSDP and create the Multiboot struct for it.
-fn handle_acpi(table: &ConfigTableEntry, info_builder: &mut InfoBuilder) {
-    debug!("handling ACPI RSDP");
+/// Parse the ACPI RSDP version 1 and create the Multiboot struct for it.
+fn handle_acpi_v1(table: &ConfigTableEntry, info_builder: &mut InfoBuilder) {
+    debug!("handling ACPI RSDP version 1");
+    let rsdp = unsafe { *(table.address as *const Rsdp) };
+    if rsdp.validate().is_err() {
+        warn!("the RSDP is invalid");
+        return;
+    }
+    if rsdp.revision() != 0 {
+        warn!("invalid RSDP revision (expected: 0, got: {})", rsdp.revision());
+        return;
+    }
+
+    info_builder.set_rsdp_v1(
+        rsdp.signature(), rsdp.checksum(),
+        rsdp.oem_id().as_bytes()[0..6].try_into().unwrap(),
+        rsdp.revision(), rsdp.rsdt_address(),
+    );
+}
+
+/// Parse the ACPI RSDP version 2 and create the Multiboot struct for it.
+fn handle_acpi_v2(table: &ConfigTableEntry, info_builder: &mut InfoBuilder) {
+    debug!("handling ACPI RSDP version 2");
     let rsdp = unsafe { *(table.address as *const Rsdp) };
     if rsdp.validate().is_err() {
         warn!("the RSDP is invalid");
         return;
     }
     if rsdp.revision() == 0 {
-        info_builder.set_rsdp_v1(
-            rsdp.signature(), rsdp.checksum(),
-            rsdp.oem_id().as_bytes()[0..6].try_into().unwrap(),
-            rsdp.revision(), rsdp.rsdt_address(),
-        );
-    } else {
-        unsafe {
-            if !RSDP_V2_SET {
-                info_builder.set_rsdp_v2(
-                    rsdp.signature(), rsdp.checksum(),
-                    rsdp.oem_id().as_bytes()[0..6].try_into().unwrap(),
-                    rsdp.revision(), rsdp.rsdt_address(), rsdp.length(),
-                    rsdp.xsdt_address(), rsdp.ext_checksum(),
-                );
-                RSDP_V2_SET = true;
-            }
-        }
+        warn!("invalid RSDP revision (expected: >0, got: {})", rsdp.revision());
+        return;
     }
+
+    info_builder.set_rsdp_v2(
+        rsdp.signature(), rsdp.checksum(),
+        rsdp.oem_id().as_bytes()[0..6].try_into().unwrap(),
+        rsdp.revision(), rsdp.rsdt_address(), rsdp.length(),
+        rsdp.xsdt_address(), rsdp.ext_checksum(),
+    );
 }
 
 /// The entry point for SMBIOS.